The present invention relates to a control system of a vehicle such as a car and an automobile using the same, particularly to a vehicle control system capable of reducing the cost of the control system and an automobile using the same.
FIG. 11 is a block diagram of a conventional vehicle control system of a car or the like.
The vehicle control system 60′ is constituted of an electronic control unit (ECU) 1′, a plurality of sensors 2′, and a plurality of actuators 3a′, in which a predetermined operation is performed by the electronic control unit 1′ set in a cabin in accordance with signals of the sensors 2′ provided in the engine room of the vehicle to drive the actuators 3a′. 
The electronic control unit 1′ is constituted of an input interface (input I/F) 11′, an arithmetic processing section 10′, and an actuator driver 4′, in which the input I/F 11′ processes signals sent from the sensors 2′ and outputs them to the arithmetic processing section 10′, the arithmetic processing section 10′ performs predetermined operations and outputs an optimum signal to the actuator driver 4′, and the actuator driver 4′ drives the actuator 3a′ serving as a load through a connector 3b′. The actuator driver 4′ is concentratedly set in the electronic control unit 1′.
In the above vehicle control system, an engine control system of a car is a system for optimally controlling an engine by performing predetermined operations by a microcomputer serving as an arithmetic processing section in an engine control unit serving as an electronic control unit in accordance with signals sent from an engine-speed sensor, a water-temperature sensor, and an intake-air-flow sensor, outputting a fuel injection signal to a driver for driving an injector and a switching signal and a valve-opening-degree adjustment signal to a driver for driving various valves and relay switches.
In the case of the vehicle control system 60′ in FIG. 11, the actuator driver 4′ is concentratedly set in the electronic control unit 1′. Moreover, there is a publicly-known example in which actuator drivers are dispersed not in an electronic control unit but by making the drivers respectively correspond to an actuator to be driven. The official gazette of Japanese Patent Laid-Open No. 79841/1996 discloses the art of a communication connector of a vehicle electronic controller for building each of the above dispersed actuator drivers in a connector connected to an actuator in order to improve the versatility of the actuator. Moreover, as other conventional examples of vehicle control systems, various arts are disclosed in the official gazette of Japanese Patent Laid-Open No. 275801/1999 and the like.
In the case of a vehicle control system, a comparatively large current (approx. several amperes) generally flows through an actuator driver when driving an actuator. The actuator driver frequently uses a power transistor or power MOS in which Joule heat is produced due to an on-resistance because the comparatively large current flows when power is turned on.
Therefore, as shown by the conventional vehicle control system 60′ in FIG. 11, when the actuator driver 4′ is concentratedly set to one place in the electronic control unit 1′, a problem occurs that the calorific value of the whole of the electronic control unit 1′ is increased by the actuator driver 4′ serving as a heat-producing part and the increase of the calorific value may affect control.
Particularly, in the case of a recent car, the above electronic control unit tends to be set not in a cabin but in a vehicle engine room in order to reduce the harness cost and assembling man-hours and thereby the electronic control unit is exposed to a severer temperature environment. Therefore, to avoid the electronic control unit from being exposed to the environment, it is necessary to use a radiation component such as a heat sink or radiation fin in order to radiate heat. Thus, a problem occurs that the manufacturing cost and the cost of the whole vehicle control system in its turn increase.
In this case, as the control system disclosed in the Japanese Patent Laid-Open No. 8-79841 (1996), it is considered to make actuator drivers respectively serving as a radiation component correspond to an actuator to be driven and disperse the drivers to the actuator side. However, it is not sufficient to merely disperse the actuator drivers because the following are indispensable for a present engine control system: a self-diagnosis function for diagnosing a trouble such as a disconnection or short circuit of an actuator and communicating the diagnosed state to an arithmetic processing section of an electronic control unit, a self-protection function for preventing an actuator driver from being broken down due to overcurrent or overheat when the above trouble occurs, and a timer circuit when PWM(Pulse Width Modulation)-controlling the dispersed actuator in a multiplex communication system through a serial communication line.
That is, the present inventor obtained the new knowledge that in the case of a vehicle control system having an electronic control unit and a plurality of actuators, it is necessary to disperse actuator drivers to the actuator side in order to reduce the cost of the vehicle control system, provide a self-diagnosis section, a self-protection section, and a communication-control section for each of the actuator drivers and make the drivers independent in order to keep the reliability and functionality of the system even after the actuator drivers are dispersed. In the case of the above prior art, however, the actuator drivers are not dispersed to each actuator side separately from the electronic control unit or the actuator drivers are not dispersed to easily radiate heat even if the drivers are set to the outside of the electronic control unit. Moreover, the drivers are not independent drivers capable of constructing an actual system. Therefore, it is not particularly considered to maintain the reliability and functionality of the control system even if reducing the radiation-component cost of the vehicle control system by reducing the heat produced in the electronic control unit and dispersing the actuator drivers.